As a point of information, if you use the NATS/AIS source for notam, you don’t need to keep a pdf copy as proof, only a note of the number of the request. They keep copies of all for a period (6 months?) so they can trace if anything was missing from a download that should have been there.
Personally, I find NATS/AIS notam easier for me to use than the graphic sources I have tried (not SD, haven’t used it) but that is a personal preference, and related to gliding (not going in straight lines).
Chris N